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Martinez-Lopez A.,Av Institute Polytechnic Nacional | Alvarez-Gomez I.G.,Av Institute Polytechnic Nacional | Perez-Cruz L.,National Autonomous University of Mexico | Verdugo-Diaz G.,Av Institute Polytechnic Nacional | Villegas-Aguilera M.M.,Av Institute Polytechnic Nacional
Journal of Sea Research | Year: 2016

Limited areas of sea floor have the physiochemical conditions that allow for the formation and preservation of high resolution (yearly or close to yearly) laminated sediments that can function as a historic proxy for past oceanographic and climate conditions. We evaluated and established the fidelity of the sedimentary record in recording these signals by analyzing silicoflagellates production, changes in species composition, skeletal settling and their subsequent burial in bottom sediments at Alfonso Basin. The data series from December 2005 to February 2008 showed similar tendencies in both the vertical flux and overlying euphotic zone (Zeu) production of silicoflagellates. Both series were numerically dominated by Octactis pulchra with maxima values being recorded for the mixed water column period. Observed differences occurred during the studied years in both magnitude and in flux composition. The presence of a mixed assemblage with (warm-temperate-cold) species such as Dictyocha fibula var. robusta, Dictyocha epiodon and Distephanus speculum could be explained by a synchronization of trends between a predominantly positive Pacific Decadal Oscillation and a positive North Pacific Gyre Oscillation climate phases that were the background conditions underlying the early 2006 through 2007 El Niño event. A Morisita's similarity index value of 97.5% between winter trap and Zeu samples combined with an annualized settling factor of 0.45, suggests that Alfonso Basin is a favorable settling environment for silicoflagellates. However, core-top sediments showed an attenuation of record fidelity (burial factor=0.25) resulting in a modified record for the production and settling of skeletons. O. pulchra that were not preserved in sediments as the dominant species and with this removal, the signal was also lost of the highest silicoflagellate production season (Mixing-cyclonic eddy periods) from the sedimentary record of the Alfonso Basin. © 2016 Elsevier B.V. Source


Mazon-Suastegui J.M.,Av Institute Polytechnic Nacional | Fernandez N.T.,University of the Republic of Uruguay | Valencia I.L.,Av Institute Polytechnic Nacional | Cruz-Hernandez P.,Av Institute Polytechnic Nacional | Latisnere-Barragan H.,Av Institute Polytechnic Nacional
Food Control | Year: 2016

Seafood marketing requires certificated products generated under sustainable management practices. The oyster farming is profitable but its identification, and hence certification is difficult due to their phenotypic plasticity. This study intends to prove that 28S rRNA has a comparable level of resolution for the correctly oyster species identification. Additionally, the resolution level of mitochondrial cytochrome c oxidase subunit I (COI) and nuclear inter-transcribed spacer 1 (ITS-1) were assessed. Under a phylogenetic approach, levels of genetic divergence intra and inter specific and nucleotide substitution saturation, were analyzed from 196 sequences of 9 oyster species belonging to the subfamilies Crassostreinae (Crassostrea gigas, Crassostrea sikamea, Crassostrea virginica, Crassostrea rhizophorae, Crassostrea corteziensis and Crassostrea columbiensis), Striostreinae (Saccostrea palmula and Striostrea prismatica) and Ostreinae (Ostrea chilensis). The results showed the higher genetic divergence for ITS-1 followed by COI and 28S. However, the substitution saturation analysis shown that the phylogenetic signal of ITS-1 was unreliable. For COI, the phylogenetic signal was moderate and problems to separate (S. palmula and S. prismatica) and obtain (C. corteziensis and C. columbiensis) haplotypes, were experienced. Finally, although the 28S showed the lower level of genetic divergence, their saturation analysis showed a reliable phylogenetic signal and correctly identify all the oyster species and clustered them by subfamily and geographic origin. Hence, the 28S fragment analyzed shown that could be used as an alternative marker and presented advantage due to its methodological simplicity and confidence for species identification. © 2016 Elsevier Ltd. Source

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